The heart rate is one of the most basic life signs of a patient. It is very important for a physician or other health care provider to have quick and accurate heart rate information when treating a patient, especially in an emergency situation. One time-honored method of obtaining the heart rate of a patient is by the auscultation and/or palpitation method, wherein the doctor, nurse, or other trained health care professional is required to feel or listen for a pulse, count the heart beats for a fixed period of time, and then calculate the pulse rate. One very familiar listening tool used for auscultation is the stethoscope. While providing the human touch, the auscultation and palpitation techniques are particularly prone to human error and further require the caregiver to focus on a counting task instead of the immediate needs of the patient. In an emergency situation, a doctor's time can be much better spent if he doesn't have to take time out to count the patient's pulse rate.
Another common technique for measuring a patient's pulse rate is by using electronic instrumentation. The heart rate may be detected by measuring rhythmic changes in the EMF potential generated by the periodic firing of the neurons of the cardiac system (electrocardiogram or ECG), by measuring vascular pressure changes coincident with the expanding and contracting of blood vessels with the heart beat (sphygmometer), and/or by measuring the changes in the Doppler shift of ultrasonic energy caused by the changes in the relative speeds of red blood cells reflecting the ultrasonic energy back at its source (Doppler ultrasound stethoscope or DUS). While more accurate than auscultation and palpitation, the above-mentioned instrumentation capable of performing these measurements tend to be bulky and cumbersome, and also require special preparations be made before measurements may be taken. Moreover, in the case of the ECG, specialized training is required to both administer the tests and to interpret the results. ECG monitors are thus found primarily in controlled clinical settings.
Currently, a patient's heart rate is either mechanically assessed in a clinical setting by bulky and expensive equipment or manually assessed in the field by a human caregiver. There remains a need for a method and apparatus for the measurement of heart rate in the field that does not require the caregiver to focus on the task of measuring the heart rate to the exclusion of other, potentially more important, tasks. The present invention satisfies this need.